The present invention relates to improvements in a servo control system in which signals are serially transmitted from a host controller to a plurality of servo amplifiers by one dedicated network.
Referring to FIG. 6, a servo control system according to the related art will be explained below. In FIG. 6, a host controller 1 for sending commands of a target position and moving speed to servo amplifiers 30, 50 includes: a sequence control section 3 for conducting creation of positioning data and the start and stop of operation; and a motion control section 10 for conducting control of the command follow-up type servo amplifier 50.
The sequence control section 3 includes: a CPU 5 for sequence control (hereinafter, referred to as a sequence CPU hereinafter) and a memory 7 for sequence control in which the content of sequence is stored. The motion control section 10 includes: a CPU 12 for motion control (hereinafter, referred to as a motion CPU hereinafter) and a memory 14 for motion control in which the content of motion is stored. Between the sequence CPU 5 and the motion CPU 12, there is provided a dual port memory 8 to which access can be made from both sides so that data can be sent and received.
An output of the sequence control section 3 is connected in series to the positioning type servo amplifiers 30-1 to 30-n, which have no interpolation control function with other shafts but have a positioning function of one shaft by conducting calculation which is not synchronized with the master clock of the host controller 1, through a communication line 20 via an interface 9 for control serial (hereinafter, referred to as I/F hereinafter). These servo amplifiers 30-1 to 30-n are connected with servo motors (not shown).
In order to make up the interpolation control function with other shafts, an output of the motion control section 10 is connected with the command follow-up type servo amplifiers 50-1 to 50-n via an I/F 16 for motion serial and a communication line 40.
In this case, the command follow-up type servo amplifier 50 operates as follows. While the command follow-up type servo amplifier 50 is synchronized with the master clock of the host controller 1, command data of a position, speed and torque are successively calculated. Then, the command follow-up type servo amplifier 50 receives the command data, controls the servo motor according to the command data, and calculates feedback data as information on control result, and then the feedback position, speed and torque are sent to the host controller
Referring to FIG. 6, operation of the servo control system configured as described above will be explained below. The sequence CPU 5 sends commands such as a target position, moving speed, setting of time constant of acceleration and deceleration, and a command of positioning activation to the positioning type servo amplifiers 30-1 to 30-n via the I/F 9 for control serial and the communication line 20.
On the other hand, the motion CPU 12 conducts a motion control calculation such as an interpolation calculation and acceleration and deceleration calculation, calculates a command data for each control period, and transmits the calculated data to the command follow-up type servo amplifiers 50-1 to 50-n via the I/F 16 for motion serial and the communication line 40.
According to the above structure, it is possible for the host controller 1 to conduct control for a plurality of servo amplifiers 30, 50, the control involving setting, changing, and reading a parameter and monitoring inside data.
The above servo control system includes the communication lines 20, 40 of two systems for the positioning type servo amplifier 30 and the command follow-up type servo amplifier 50. Therefore, compared with a communication line having one system, the number of I/Fs for serial and connectors therefor is increased.
Accordingly, it is possible to consider a structure in which the servo amplifiers 30, 50 are connected in series to each other and the communication line is formed into one system so that the number of I/Fs for serial can be decreased.
However, in the above servo control system composed of one system of communication line, the following problems may be encountered. When each frame having an address corresponding to each servo amplifier 30, 50 is sent from the host controller 1 by serial communication, the frame transmitting time is increased by the dead time or the like between the frames.
The present invention has been accomplished to solve the above problems. It is an object of the present invention to provide a simple servo control system which conducts controlling by mixedly using a positioning type servo amplifier and a command follow-up type servo amplifier.
A servo control system according to a first aspect comprises:
a host controller having a master clock, which is a reference of communication, the host controller for sending a command;
a first servo amplifier controlled based on the command sent from the host controller, the first servo amplifier having a calculating function, which is not synchronized with the master clock;
a second servo amplifier controlled based on the command sent from the host controller, the second servo amplifier having a calculating function, which is synchronized with the master clock; and
serial transmitting means for serially transmitting one frame at once, which is the command, having discrimination data indicating the first or the second servo amplifier and control information of the first and the second servo amplifiers in an information section into which information to be transmitted is inputted and serially transmitting from the host controller to the first and the second servo amplifier,
wherein the first and second servo amplifiers comprise information section reading means for recognizing a local station and reading content of the information section after the discrimination data of the frame based on the local station and the discrimination data of the frame.
By the controller which serves as rewriting means of the frame, the frame information section can be rewritten from the control information of the first servo amplifier to the control information of the second servo amplifier together with the discrimination data and on the contrary, the frame information section can be rewritten from the control information of the second servo amplifier to the control information of the first servo amplifier. Therefore, while the first and the second amplifiers are connected with the same communication line, the servo amplifier can be flexibly changed according to an object to be controlled.
Therefore, even when the first and the second amplifiers are mixed arranged on the same communication line by one frame, the servo amplifier can be flexibly changed according to an object to be controlled.
The servo control system according to a second aspect, comprises a plurality of the first or the second servo amplifiers,
wherein the first or the second servo amplifiers includes:
a reference servo amplifier for communicating by a reference communication period generated based on the master clock;
a multiple time servo amplifier for communicating by a communication period which is multiple times as long as the reference communication period; and
communication switching means for communicating with the multiple time servo amplifier every multiple times of the reference communication period.